Recently, secondary batteries are widely used in mobile devices such as notebooks, mobile phones, etc., various power systems such as electric bicycles, electric vehicles, hybrid vehicles, etc., power backup systems for supplying backup power in the event of a power outage, large-capacity power storage devices for storing large amounts of power and supplying the stored power to other devices, etc.
Among various types of batteries, a battery using lithium is most widely used for its high energy density, high operating voltage, and long life span.
A secondary battery is used in combination with a battery management system (BMS). The battery management system serves to control the charge and discharge of the secondary battery to an appropriate level and to stop the charge or discharge of the secondary battery in the event of an abnormal situation such as overdischarge, overcharge, overcurrent, etc., thereby preventing explosion or deterioration in performance of the secondary battery.
A secondary battery management apparatus includes a microprocessor that receives power from the secondary battery to perform the above-described operations. The microprocessor does not consume a large amount of power per unit time and thus maintains its operating state even when the secondary battery is no longer in use. That is, even when the secondary battery is not in a charge or discharge mode, the microprocessor monitors the voltage, current, temperature, etc. of the secondary battery and continues to maintain the management operation. Therefore, when the secondary battery is not being used for a long period of time, the state of charge (SOC) of the secondary battery is continuously reduced by the power consumption of the microprocessor.
The reduction in SOC is not preferable in terms of unnecessary power consumption. This is because, when the secondary battery is not in the charge or discharge mode, the operation of the secondary battery management apparatus is not in fact required. Moreover, the reduction in SOC of the secondary battery may cause an overdischarge state of the secondary battery. For example, when the secondary battery is manufactured, the secondary battery is charged to a predetermined SOC (for example, 30%). However, after the secondary battery is manufactured, if the secondary battery is stored in a warehouse or export container for a long time or if the use of the secondary battery is delayed due to a long distribution period, the power of the secondary battery is exhausted by the secondary battery management apparatus, and thus the secondary battery reaches the overdischarge state.
Therefore, in the technical field to which the present disclosure pertains, a technique for controlling the supply and cutoff of operating power to the secondary battery management apparatus by detecting the time when the charge and discharge of the secondary battery should be monitored is required.